Prior to the present invention, the closest prior art to which this invention is directed is the inventor's own U.S. Pat. No. 3,450,299 which is directed to wedge-like projections extending about radially inwardly from the lateral inner walls of a cap, with the projections being molded as an integral part of the cap itself and extending downwardly from the upper inner surface of the top of the cap, this heretofore being a result of the sole known method of making the caps of this type, as well as lack of insight in the art as to how to better even-surfaced top outer walls as contrasted to the uneven upper outer top wall with its multiple sinks therein. These sink marks of prior caps of this type make it difficult if not impossible to print satisfactorily any pertinent information or sales or identifying data or design thereon because of the uneven surface brought about by the contraction of cooling plastic at the points of union of the inner wedge-like projections with the inner top wall of the cap during the injection molding thereof.